Roger Wolfson, a former Senate Staffer, spent four years working for a US Senator (Paul Wellstone) who was ultimately killed in a plane crash. Roger’s reaction was to sell all his possessions, buy a sailboat, and sail twenty thousand miles. During this time at sea, he wrote this essay about the parallels between flight and sailing.
Sailing is a wonderful metaphor for living a good life. It’s all about balance. A sailboat has no moving parts, and yet by placing itself in a harmonious relationship between the natural forces of current and wind, it will take you around the world.
The first and most challenging element to understand about sailing is how sails themselves function. How a sailboat can sail with the wind blowing from behind it is simple and needs no explanation. The wind fills the sails and pushes against them, and an efficient boat can travel almost as fast as the wind itself.
But how can a sailboat sail toward a source of wind, often at a pace faster than the wind itself?
If the answer to this question eludes you, you are not alone. It was a principle humans didn’t really decipher until shockingly recently in our history, and it was the full appreciation of this principle that led us to be able to make planes fly.
Planes fly because of the shape of their wings. Not the length of the wing, not the distance from front to back of the wing, but the shape of its width matters most.
A plane’s wing is flatter on the bottom and rounder on the top, like a capitol letter D lying on its left side.
Why does this matter?
At high speeds, air behaves like a fluid. Fluid dynamics are very interesting, because a fluid is actually a tangible, almost living thing. A fluid has a balance, and if disturbed, it tries to return to that balance. When a plane is pushed forward by its engines, the edge of the wing strikes the wind, breaking the wind in half. The wind rushes above and below the wing like cars going left and right around a divider at the center of a road. Fascinatingly, because the air at that speed is like a fluid, the air going above the wing has to meet up with the air going below the wing at the very moment the wing finishes passing through it. Think of a knife slicing through jello. The knife slices between two jello molecules. Once the knife has finished passing through the jello, those two molecules will line up again, thanks to the pressure of the jello on the other sides of the two molecules, pushing them back together. So it is with two air molecules cut apart by a wing.
OK. The wing strikes the air, splitting it in half. Molecules that were once touching each other are now on opposite sides of a wing. Pressure above and below these molecules pushes them back together, but first they have to get around this wing. But because of the way the wing is shaped, the wind has to travel at different speeds to meet up at the other side. The wing is gently curved on the bottom, so the wind speeds up a bit like a car accelerating to pass another car. Meanwhile, the wind going over the top of the wing has to speed up a lot to get all the way around the larger curve, like a car speeding up to pass a truck.
The wind under the wing, therefore, moves more slowly, creating (on a molecular level) a traffic jam compared to what’s going on above the wing. The ‘traffic jam’ below is denser than the fast movement above, and therefore all those ‘cars’ (air molecules) exert pressure below the wing (lifting it) and the lack of ‘cars’ above the wing create a vacuum (sucking the wing upward). That’s why planes fly. As long as wind is moving fast enough against the surface of the wings, there is tremendous pressure from above and below lifting the plane up.
A sail isn’t shaped exactly like a wing. It’s shaped more like the letter C. As you can see by looking at that letter, the inner curve is shorter than the outer curve. Now, if wind strikes a sail directly from behind, the air presses only against the inner side of the sail. With pressure on only one side, the sail acts as if it were a watermelon seed simply tossed in the air. That’s why a sailboat with the wind behind it can’t go faster than the wind itself. In that case, the sail is just a parachute, catching wind. It’s not operating like a wing, and Bernouli’s principle hasn’t kicked in.
But if a sailboat heads toward the wind and the sail’s leading edge strikes the wind, dividing the wind so the air rushes along both sides of the sail, then the sail is like a watermelon seed that you squeeze tightly between your fingertips until it shoots forward.
Literally, a sailboat that wants to go fast heads directly into the wind, then turns slightly to the left or the right, allowing wind to rush faster on the outer side of the sail than the inner. The vacuum on the outer side sucks the sail in that direction, exactly the way a wing sucks a plane upward.
So why does a sailboat sail forward, rather than to the side?
There are two reasons. One is that the sail isn’t really shaped like a “C” as much as it is shaped like the number 9. The number nine curves most dramatically at the top, right? If you put the number 9 in a wind tunnel, the wind going around it will move fastest around the part that curves most, which on a nine is the upper right hand part, and on a sailboat, is the part of the sail toward the front of the boat. So the shape of the sail, with the curve closest to the leading edge of the boat, creates the greatest vacuum toward the front of the boat, pulling her forward.
Still, a lot of pressures (vectors) push the boat laterally. The second reason a sailboat moves forward rather than to the side is its keel, (like an underwater fin), which keeps it on track. Think of how iceskates sink into ice, keeping a skater moving in a straight line. Literally millions of pressures are exerted on a sailboat, pushing it in many directions. But the boat is designed to cancel out all the forces but those moving it forward. The more effectively a boat does this, the faster it goes forward.
This application of the Bernoulli Principle on sea and in air was among the greatest advances in transportation humans have ever made. For centuries, the towering, imposing sailboats upon which the entire world depended on for trade, defense, and survival, were crippled by the direction of the wind. And flying machines – they were fantasy.
Metaphorically, the lesson to me is clear. The Toist principle of “Wu” teaches us to pursue the “middle way.” Not to try to harbor, sit on, or fight against the forces of our lives, but to ride crests of waves, to glide between competing forces, and find a higher path. Don’t fight the current — ride it. Don’t catch the wind; sail it.
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